I'm making a Super Smash Bros Cinematic Multiverse fan-fic, and firstly I had one thought: third-parties accepted, but Kingdom Hearts will NOT enter. Beside law things, narratively just wouldn't fit due to the Disney fact. But later, I changed plans:
1-It's a fan-fic, bro
2-Why it must be adapted, when I can just reimagine?

Now, from this idea, I have an ask for you guys: How would be the saga if it were a Square x Nintendo crossover, instead of Disney?
Like, in the elevator where it all started, instead of two workers from Square and Disney having met, one from Square and another from Nintendo would have entered at the same time and they would have chatted for a while. I know there's the Mario RPG thing, but dreaming doesn't cost anything.
I imagine a Hero's Shade secret boss fight (the spirit of the Hero of Time, the Ocarina of Time/Majora's Mask Link) being the Lingering Will equivalent, and other characters such as Roxas, Aqua or Riku would be in Smash.